On Sat, 2017-06-17 at 19:22 +0530, Vignesh R wrote:
> DMA RX completion handler for UART is called from a tasklet and hence
> may be delayed depending on the system load. In meanwhile, there may
> be
> RX timeout interrupt which can get serviced first before DMA RX
> completion handler is executed for the completed transfer.
> omap_8250_rx_dma_flush() which is called on RX timeout interrupt makes
> sure that the DMA RX buffer is pushed and then the FIFO is drained and
> also queues a new DMA request. But, when DMA RX completion handler
> executes, it will erroneously flush the currently queued DMA transfer
> which sometimes results in data corruption and double queueing of DMA
> RX
> requests.
>
> Fix this by checking whether RX completion is for the currently queued
> transfer or not. And also hold port lock when in DMA completion to
> avoid
> race wrt RX timeout handler preempting it.
> static void __dma_rx_complete(void *param)
> {
> - __dma_rx_do_complete(param);
> - omap_8250_rx_dma(param);
> + struct uart_8250_port *p = param;
> + struct uart_8250_dma *dma = p->dma;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&p->port.lock, flags);
> +
> + /*
> + * If the completion is for the current cookie then handle
> it,
> + * else a previous RX timeout flush would have already pushed
> + * data from DMA buffers, so exit.
> + */
> + if (dma->rx_cookie != dma->rxchan->completed_cookie) {
Wouldn't be better to call DMAEngine API for that?
dmaengine_tx_status() I suppose
> + spin_unlock_irqrestore(&p->port.lock, flags);
> + return;
> + }
> + __dma_rx_do_complete(p);
> + omap_8250_rx_dma(p);
> +
> + spin_unlock_irqrestore(&p->port.lock, flags);
> }
>
> static void omap_8250_rx_dma_flush(struct uart_8250_port *p)
--
Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Intel Finland Oy
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